1. Field of the Invention
The present invention relates to a method for manufacturing a reinforcing structure for tyres of vehicles, comprising the following steps: preparing strip-like segments each comprising longitudinal filiform elements arranged mutually parallel at least partially coated by at least a layer of elastomeric material; applying the strip-like segments in mutually approached relationship along the circumferential development of the toroidal support, to form at least a reinforcing layer having continuous circumferential development about a geometric axis of rotation.
The invention further relates to an apparatus for implementing the aforementioned method, said apparatus being of the type comprising: a unit for the feeding of strip-like segments arranged mutually parallel at least partially coated by at least a layer of elastomeric material; a laying unit for applying each of said strip-like segments onto a toroidal support, according to a pre-set laying angle relative to a direction of circumferential development of the toroidal support itself; first angular actuation devices to determine a relative motion between the laying unit and the toroidal support, about a geometric axis of the toroidal support itself.
In the course of the present description, the invention shall be illustrated with particular reference to the manufacture of a belt structure of a tyre. It is however hereby specified that the method and the apparatus according to the invention can be employed to manufacture a carcass structure of the tyre or, more generally, any other reinforcing structure, comprising cords oriented in mutually parallel fashion and/or according to a pre-set angle relative to an equatorial plane of the tyre.
2. Description of the Related Art
A tyre for vehicle wheels normally comprises a carcass structure essentially composed by one or more carcass plies shaped according to a substantially toroidal configuration and presenting its axially opposite lateral edges engaged to respective annular reinforcing structures incorporating circumferentially inextensible inserts, usually called “bead rings”. Each annular reinforcing structure is incorporated in a so-called “bead” defined along an inner circumferential edge of the tyre for the anchoring thereof to a corresponding mounting rim.
On the carcass structure is applied, in radially external position, a belt structure comprising one or more belt layers shaped in a closed loop, essentially composed by textile or metal cords suitably oriented relative to each other and relative to the cords belonging to the adjacent carcass plies.
In a position radially external to the belt structure is also applied a tread band, normally constituted by a strip of elastomeric material of adequate thickness. It should be specified that, for the purposes of the present description, the term “elastomeric material” means the rubber compound in its entirety, i.e. the set formed by at least a polymeric base suitably amalgamated with reinforcing fillers and/or process additives of various kinds.
On the opposite sides of the tyre is applied a pair of sidewalls each of which covers a lateral portion of the tyre lying between a so-called shoulder area, located in proximity to the corresponding lateral edge of the tread band, and the corresponding bead.
In the manufacturing processes of less recent design, each belt layer is formed by joining sequentially a plurality of segments obtained by cutting to measure a continuous strip composed by a plurality of parallel longitudinal cords incorporated in an elastomeric layer. More in particular, the cutting and joining operations are performed in such a way as to obtain a so-called belt ring, wherein the cords of each segment are oriented according to a predetermined inclination relative to the circumferential development of the ring itself and parallel to the cords of the contiguous segments.
The completed belt ring, which can also comprise two or more layers formed in succession in radial superposition relationship, is associated in radially external position to the carcass structure, normally simultaneously with an operative step wherein the latter, initially obtained in the form of a cylindrical sleeve, is shaped according to a toroidal configuration.
Recently, particular attention has been dedicated to the search for manufacturing methods which would allow to eliminate or at least limit the manufacture of intermediate semi-finished products required for the manufacture of the tyres. For instance, in the European patent application EP 97830731.2, in the name of the same Applicant, a method for manufacturing tyres is described wherein the carcass ply or plies, as well as each of the belt layers, are obtained by laying, one after the other in circumferential approach relationship, a plurality of strip-like segments onto a toroidal support shaped according to the internal conformation of the tyre to be obtained.
Document WO 99/17920 describes a method and an apparatus for manufacturing a belt layer by the laying of strip-like segments cut off from a continuous strip-like element. Each segment, once cut off from the continuous strip-like element, is drawn by means of magnetic or suction-cup gripping organs, commanded by one or more robot arms. The gripping organs hold the strip-like segment in correspondence with its opposite extremities, and possibly in correspondence with its central section, and are actuated upon command from the robot arms to cause the application of the segment itself onto the exterior surface of a toroidal support, according to a predetermined angle relative to the circumferential development thereof. Once the application is complete, the toroidal support is made to rotate about its own geometric axis according to a predetermined angle, to allow the application of a new strip-like segment adjacently to the one applied previously. The sequential repetition of the steps described above causes the formation of a belt layer extending according to the entire circumferential development of the toroidal support.